Precise knowledge of a patient's anatomical structures is a basic requirement for effective and correct diagnosis and treatment of diseases. However, human anatomy varies considerably from patient to patient, and the relative positions of anatomic structures can be altered by injury, disease processes (displacement by tumor or inflammation), and previous operations. Conventional imaging techniques used to determine the positions of anatomical structures include computerized axial tomography scanning and magnetic resonance imaging which are excellent for anatomic localization, but the techniques are only available using machines which are large and expensive, and consequently, require special facilities for use and operation. Further, these machines are not readily available at the bedside of the patient or in the operating room. Therefore, a more desirable alternative is needed whereby the position of anatomical structures can be more readily ascertained without the use of these expensive and cumbersome machines.
Pregnant women routinely undergo pelvic examinations during labor and delivery to monitor certain parameters that are important for a successful birth of the child and survival of the mother. A pelvis that is too small to allow delivery of the fetus can lead to complications during delivery, including loss of the fetus and, in some cases, complications leading to loss of life of the mother. One method for determining the size of the pelvis is based on guesswork and experience where palpation of the pelvic bone is performed using the index and middle fingers. Other methods are pelvimetry which is performed by x-ray which may contain potentially harmful radiation, or by ultrasound which is somewhat cumbersome and expensive.
Another preparatory procedure during labor and delivery is the repeated manual examination of the dimensions of the cervix during its progressive dilation to allow passage of the fetus. Current measurements are done digitally using the index and middle fingers. This repeated examination increases the incidence of infection in the fetus and mother. Therefore, a less invasive procedure is desirable to reduce the risk of infection and to more accurately track the size of the cervix during the birthing process.
When surgery is required, the potential for complications is heightened by the inadvertent damage to veins, arteries, and ducts. Surgery can be particularly hazardous when there is inflammation due to infections, scar tissue, fibrosis due to previous surgery, or distortion of anatomy due to tumors. For example, the pelvis contains the ureter, and the iliac artery and vein in close proximity to the other pelvic organs such as the uterus, ovaries, intestines, and bladder, which often require surgical treatments. In the presence of inflammation and scar tissue, surgery in this area can be quite hazardous because of the potential injury to the ureter, and the iliac artery and vein which can be encased and distorted. Similarly, the structures of the biliary system, consisting of the gallbladder, the common bile duct, and the portal vein, often become inflamed secondary to obstruction and infection, and surgical resection of the gallbladder and/or exploration of the common bile duct are necessary to treat such disease processes. During such surgery, injury to the common bile duct and the adjacent portal vein occurs too frequently. Such complications can be disastrous to the patient. Therefore, a method of accurately determining the position of veins, arteries, and ducts in relation to the cutting instrument is crucial during surgery in order reduce the potential for hazardous or even fatal complications due to the damage of these vital structures.
The position sensors may also be used to detect movement or displacement of structures. For example, position sensors can be positioned over the ribs or intercostal muscles to detect movement during respiration. In addition, position sensors can be temporarily affixed to bone intraoperatively to allow correct positioning of artificial limbs or joints. Current methodology for alignment of hip joints requires manual and visual means leading to malalignment, a major cause of morbidity in patients undergoing this procedure.
Position sensors and accelerometers are vital components for stereotactic surgery instruments utilized in neurologic, ophthalomoligic, orthopedic, and laparoscopic surgeries. The disclosed sensors allow for precise positioning and guidance of surgical instruments in critical areas. The miniature size of the ball position sensor allows for smaller instrumentation and less damage to vital structures.